The CardioMetrix Endoluminal HF Monitoring System is intended to provide patients with ambulatory monitoring their heart function, allowing for better management of their disease and allowing them to live a life less encumbered by HF. The system uses ultrasound to determine pulmonary arterial blood pressure and flow. Using these two parameters, calculations are made to determine cardiac dynamics, such as pump power. With these data, physicians and patients will become aware of acute changes in HF and will be able to make earlier changes in HF management and treatment, preventing acute decompensation. The implant is passive, receiving energy and transmitting the flow and pressure data out of the body using RF communications. Therefore, the implant will not require a battery, with limited life, to accomplish these tasks. The implant has 4 ultrasound sensors to determine flow and a separate sensor for measurement of pressure. The sensors will be mounted on a self-expanding frame that will be deployed in the pulmonary artery using standard catheterization techniques during an outpatient procedure. Once deployed, the carrier will provide correct sensor orientation with respect to the blood flow. An external hand-held unit will be used to energize and collect data from the implant, with a display showing pressure, flow and cardiac power, measures of cardiac performance. In phase I of this SBIR, sensor prototypes will be modified to work wirelessly and will be tested acutely in animals. In phase II, a fully functional wireless implant will be developed, fabricated and tested in animals. Development activities include the integration and miniaturization of the circuitry needed to power the endoluminal implant, obtain the flow and pressure data and provide outbound communications of the data. Heart Failure (HF) is a chronic and progressive disease affecting an estimated 5 million Americans and 23-27million people worldwide. Nearly 600,000 new cases are diagnosed annually in the US, and 2.5-3 million are diagnosed worldwide. We propose a novel hemodynamic monitor that may reduce the cost of care, the morbidity, and the mortality of patients with HF.